Strong nonwoven fabrics from engineered multiconstituent fibers

ABSTRACT

The present invention provides a thermally-bonded nonwoven fabric that is made from a web which comprises from 100 to 5 percent by weight of multiconstitutent fibers. The multiconstituent fibers are composed of highly dispersed blends of at least two different immiscible thermoplastic polymers and have a dominant continuous polymer phase with at least one noncontinuous phase dispersed therein. The noncontinuous phase exists as an elongated fibrillar polymer domain oriented generally in the direction of the fiber axis. No single polymer domain cross-section of said noncontinuous phase or phases is larger than 0.1% of the cross-sectional area of said fiber. The polymer of the noncontinuous phase or phases has a Polymer Melt Temperature (PMT) at least 30° C. below the PMT of the continuous phase. The fiber is configured such that the noncontinuous phase or phases occupy a substantial portion of the fiber surface. In addition to such fabrics, laminates--made by combining nonwoven fabrics made from the materials and processes as described herein with films, paper, tissue, woven fabrics, or nonwoven fabrics such as meltblowns--are also contemplated. The fabric according to the invention readily bonds to other materials of the sorts mentioned, and is therefore suitable for use in filtration media, medical and clean room garments, CSR wrap, absorbent article backsheets, and other barrier structures.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to nonwoven fabrics made by thermally bondingfibrous webs made from certain types of multiconstituent fibers, and tolaminates incorporating said fabrics. Thermal bonding of the nonwovenfabrics may be accomplished by calender or `through air` techniques orultrasonically. The multiconstituent fibrous webs may contain otherfibers in addition to the thermoplastic multiconstituent fibers. Thenonwoven fabrics produced according to the present invention may beoptimized as to softness and strength characteristics.

2. Description of the Prior Art

Structured multicomponent fibers--made by coextrusion of differentpolymers in a variety of structured configurations--have long beenwell-known. Some relevant references are: Davies (U.S. Pat. No.3,595,731), Gerlach (U.S. Pat. No. 4,361,609), Kiriyama (U.S. Pat. No.4,568,506), and Uchikawa (U.S. Pat. No. 4,770,925).

A few references cite fibers and nonwoven fabrics made from polymerblends wherein the dominant continuous phase is lower melting than isthe dispersed noncontinuous phase; see Kubo (European Patent ApplicationNo. 0277707), Wincklhofer (U.S. Pat. No. 3,620,892) and Vassilatos (U.S.Pat. No. 4,632,861). By definition, to thermally bond such fibers,portions of the continuous fiber phase are raised to temperatures wherepartial molecular relaxation of the continuous lower melting phaseoccurs. Relaxation occurs not only at the bond site proper but also inthe fiber region surrounding the bond site which is responsible fordistributing a load or strain throughout the bonded fiber network.Although thermally-bonded nonwoven fabrics can be made from thesematerials, strength is compromised.

Some instances are also known wherein blends of different polymers areextruded from the orifices of spinnerets in order to make fiberscontaining "free form" microfibrils which can then be separated from thematrix polymer: Breen (U.S. Pat. No. 3,382,305), Twilley (U.S. Pat. No.3,369,057), and Allan (U.S. patent application Ser. No. 07/220,203).

Finally, Graham U.S. Pat. No. (4,769,279) refers to meltblown fibers andfabrics made from blends of ethylene/acrylic copolymer with a secondfiber-forming polymer such as a polyvinyl, a polyamide, and apolyolefin. Graham does not disclose thermally-bonded nonwoven fabricsfrom engineered fibers, however. Furthermore, the Graham disclosure islimited to blends based upon low viscosity ethylene/acrylic copolymers.

SUMMARY OF THE INVENTION

The present invention provides nonwoven fabrics made of engineeredmulticonstituent fibers. By "engineered" fibers, we mean oriented fibersmade by melt-spinning blends of two or more immiscible polymers that arehighly dispersed and that contain a dominant continuous phase which issubstantially higher in melting point than the discontinuous phase orphases.

The present invention provides a thermally-bonded nonwoven fabric havinga basis weight in the range of 5 through 100 g/m² that is made from aweb which comprises from 100 to 5 percent by weight of amulticonstituent fiber having a fineness of 5 to 50 microns and up to 95percent by weight of other fibers. Said multiconstituent fiber iscomposed of a highly dispersed blend of at least two differentimmiscible thermoplastic polymers and has a dominant continuous polymerphase and at least one noncontinuous phase dispersed therein. Thenoncontinuous phase exists as an elongated fibrillar polymer domainoriented generally in the direction of the fiber axis. The mean of thepolymer domain cross-sections of said noncontinuous phase or phases isless than 0.1% of the cross-sectional area of said fiber. The polymer ofthe noncontinuous phase or phases has a Polymer Melt Temperature (PMT)at least 30° C. below the PMT of said continuous phase. The fiber isconfigured such that said noncontinuous phase or phases occupy asubstantial portion of the fiber surface.

In addition to the fabrics described above, laminates--made by combiningnonwoven fabrics made from the materials and processes as describedherein with films, paper, tissue, woven fabrics, or nonwoven fabricssuch as meltblowns--are also contemplated. The fabric according to theinvention readily bonds to other materials of the sorts mentioned, andis therefore suitable for use in filtration media, medical and cleanroom garments, CSR wrap, absorbent article backsheets, and other barrierstructures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photomicrograph of a cross-section of a 20-micron-diameterfiber enlarged 25,000 times.

FIG. 2 is a graphic comparison of tensile strengths versus temperaturefor various fibers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Biconstituent or multiconstituent fibers that may be used to makefabrics according to the present invention are those which are spun froman intimately-mixed blend of different polymers in which at least two ofthe polymers in the blend are immiscible. The choice of polymers islimited to those that are thermoplastic (including many elastomers) andthat have a melt temperature below 350° C., preferably below 275° C.Examples of polymers that can be used are:

Polyethylenes:

Low density PE (0.90-0.940 g/cc)

Long-chain branched PE

LLDPE (made with C₃ -C₁₀ alpha-1-olefin copolymers or4-methyl-1-pentene)

Medium and high density PE (0.940-0.960 g/cc)

Homopolymer or with copolymers described above

Atactic polypropylene

Polypropylene (at least 90% isotactic)

Block copolymers of ethylene and propylene

Random copolymers of ethylene and propylene

Polybutylene

Poly(4-methyl-1-pentene) [TPX]

Polycarbonate

Polyesters, e.g. poly(oxyethyleneoxyterephthaloyl)

Polyamides, e.g. poly(imino-1-oxohexamethylene) [Nylon 6] andpoly(iminohexamethyleneiminoadipoyl) [Nylon 66]

Poly(oxymethylene)

Polystyrene

Styrene copolymers, e.g. styrene acrylonitrile [SAN]

Polyphenylene ether

Polyphenylene Oxide [PPO]

Polyetheretherketone [PEEK]

Polyetherimide

Polyphenylene Sulfide [PPS]

Poly(vinyl acetate) [PVA]

Poly(methyl methacrylate) [PMMA]

Poly(methacrylate) [PMA]

Ethylene acrylic acid copolymer

Polysulfone

The biconstituent or multiconstituent fibers that make up a significantportion of the webs to be thermally bonded according to the presentinvention must exhibit a high degree of dispersion. In principle, themean of the cross-sectional areas of the noncontinuous phase or phasesis less than 1/1000th of the cross-sectional area of the fiber. Factorswhich determine the level of dispersion and phase morphology of thedispersed phase or phases in blend fibers are discussed in detail by D.R. Paul in "Polymer Blends", volume 2, chapter 16. Briefly, thedispersed-phase morphology of the blend fiber is dependent upon therelative rheologies of the blend components, the interfacial tensionbetween the two or more phases, the polymer volume ratio, and the threestages of the blend melt preparation and processing: melt dispersion,extrusion, and extrudate draw-down prior to solidification. In general,the largest domains in the blend will exist when the polymer ratio isnear 1.0; at this point the polymers are nearly co-continuous. Thedomain size of the discontinuous phase will decrease as the ratiodeviates from 1.0, given that the quantity of work `mixered` into theblend and the melt-spinning conditions remain constant.

Thermal bonding work on fabrics made from biconstituentpolyethylene/polypropylene staple fibers has demonstrated weak bondingat calender temperatures at and just above the melting point of thelower melting polyethylene constituent. One of the problems withbiconstituents in general in thermal bonding can be that the lowermelting component is distributed throughout the fiber matrix rather thanbeing concentrated at the surface where it can be active in bonding.Therefore fibers according to the present invention are often preferablyfibers with increased surface-to-volume ratios, with the ultimate beinga ribbon-shaped fiber. High surface/volume fibers make more of the lowermelting component available for bonding, which ultimately results inhigher tensile strength fabrics and laminates.

FIG. 1 is a TEM photomicrograph of a RuO₄ -stainedpolyethylene/polypropylene fiber cross-section, enlarged 25,000 times.The dark domains are polyethylene (PE); the lighter domains are thecontinuous polypropylene (PP) phase. The photograph demonstrates howwell the PE phase is dispersed in the PP phase. It is interesting tonote how the PE phases become circumferentially elongated at the fibersurface.

Fibers used to make fabric in accordance with the present invention maybe processed as follows: two or more polymers, selected to meet themelting point differential that characterizes the present invention, arecombined and blended to form a dispersion. The dispersion is thenemitter melt-spun into fibers, which may be formed into webs forinstance by carding, airlaying, or wetlaying, or melt-spun directly intofibrous webs by a spunbonding process. The webs are thenthermally-bonded to transform them into strong soft biconstituent-fibernonwoven fabrics. The specific fabric characteristics will be dependenton the choice of precursor fiber and processing conditions. Saidnonwoven fabrics may then be laminated into structures having a varietyof desirable end-use characteristics.

Appropriate combinations of polymers combined to make the fibers used inaccordance with the present invention are intimately blended beforebeing melt-spun into fibers or fibrous webs. A high degree of mixing isnecessary in order to prepare blends that will satisfy the degree ofdispersion criteria that characterizes the fibers used according to thepresent invention. Among the commercially available mixers that can beused are the Barmag 3DD three-dimensional dynamic mixer supplied byBarmag AG of West Germany and the RAPRA CTM cavity-transfer mixersupplied by the Rubber and Plastics Research Association of GreatBritain.

An example of an immiscible blend according to the present invention isa supermixed blend of linear low density polyethylene withpolypropylene.

Thermally-bonded nonwoven fabrics according to the present inventionexhibit advantages over similar homofilament-based nonwovens. A few ofthose advantages are higher tensile strength/basis weight ratio, andhigher tear resistance/basis weight ratio. Many of these advantages aremade possible by the fact that the lower melting component of the fibersused according to the present invention effects bonding at conditionsthat do not cause `relaxation` or loss of molecular orientation of thehigher melting component. Typically, fiber used for thermally-bondedcoverstock is not highly oriented. Highly oriented polypropylene, forexample, is difficult to bond thermally without loss of molecularorientation in the individual filament. In addition, fabrics made fromhighly drawn polypropylene are harsh and possess poor `hand`. Thefilaments described by the present invention can be highly drawn toimpart high tenacities and then thermally bonded into a nonwoven fabricwith essentially no loss of individual filament tenacity. The retentionof individual filament tenacity improves the strength properties of thefabric. Selection of the appropriate polymer (polyethylene for example)as the bonding constituent yields a fabric with greater softness thanits homofilament counterpart.

The process for manufacturing the webs to be thermally or sonicallybonded according to the present invention can be any of the knowncommercial processes for making nonwoven fabrics, including processesthat use mechanical, electrical, pneumatic, or hydrodynamic means forassembling fibers into a web, for example carding, wetlaying,carding/hydroentangling, wetlaying/hydroentangling, and spunbonding.

EXAMPLE 1

Biconstituent staple fiber was prepared by dry blending 40% by weight ofan ethylene/1-octene linear low density polyethylene [LLDPE] having amelt index of 26.5 and a density of 0.940 grams/cc with 60% by weight ofcontrolled rheology polypropylene [PP] having a melt flow rate of 26.The dry blend [PP/LLDPE] was fed into a single-screw extrusion systemequipped with a Barmag 3DD intensive mixer. Filaments were extruded anddrawn to a final denier per filament of approximately 2.0. Line speedsand cold draw ratios were adjusted to produce two filament samples, onehaving 2X cold draw and another having 3.5X draw. Refer to Table I,samples 8319-2 and 8319-3, respectively.

One gram samples of each fiber type were formed into a web using alab-scale carding device. The carded webs were then bonded on aBeloit-Wheeler lab top calender using a 16%-diamond-bond pattern and anip pressure of approximately 400 PLI. Strip tensile strengths weredetermined for samples bonded over a range of temperatures. Carded websmade from Hercules T-185 polypropylene fiber served as a control. Thebiconstituent-based fabrics demonstrate superior tensile properties overthe polypropylene homofilament-based fabric (see Tables II, III, and IV,and FIG. 2).

EXAMPLE 2

Both polypropylene and PP/LLDPE dry blend samples were (separately) fedinto a single-screw extrusion system equipped with a Barmag 3DDintensive mixer. Filaments were extruded and drawn to a final denier perfilament of approximately 2.0. Line speeds and cold draw ratios wereadjusted to produce filament samples having 2X draw. Refer to Table I,samples 8319-1A and 8319-2, respectively.

Each fiber sample was separately carded and thermally bonded on a36-inch-wide semicommercial line. Physical properties were thendetermined for the fabric samples. Data in Table V. The biconstituentfiber-based fabrics exhibited superior strip and grab tensiles, energiesat yield (TEA), and tear values.

EXAMPLE 3

Staple biconstituent fiber containing 1% by weight of asubstituted-sorbitol nucleating agent was prepared from dry blends ofPP/LLDPE that was fed into a single-screw extrusion system equipped witha Barmag 3DD intensive mixer. Filaments were extruded and drawn to afinal denier per filament of approximately 2.0. Line speeds and colddraw ratios were adjusted to produce filament samples having 3.5X draw.Refer to Table I, sample 8319-7.

The fiber was carded and thermally bonded on a 36-inch-widesemicommercial line. Data in Table VI. The strip and grab tensiles,energies at yield, and tear values were superior to a similar fibersample without nucleating agent.

EXAMPLE 4

Biconstituent fiber 8342 was prepared from a dry blend of 40% by weightof an ethylene/1-octene copolymer [LLDPE] having a melt index of 50 anda density of 0.925 g/cc with 60% by weight of controlled rheologypolypropylene [PP] having a melt flow of 35. Multiconstituent fiber 8343was prepared from a dry blend of 40% by weight LLDPE having a melt indexof 50 and a density of 0.925 g/cc with 55% by weight of controlledrheology PP having a melt flow of 35 and with 5% by weight ofethylene/acrylic acid copolymer [EAA] composed of low densitypolyethylene having a melt index of 300 and an acrylic acid content of20%. Melt blends were then separately prepared and extruded andpelletized using a single screw extruder equipped with a 6 row Rapracavity-transfer mixer (CTM) and a strand die cutter. The polymer-blendpellets were then separately re-extruded into filaments and melt-drawnto a final denier per filament of 1.9 and 2.7, respectively.

One gram samples of each fiber type were formed into webs, bonded, andtested as described in Example 1. Filament and fabric tensile propertiesare indicated in Table VII.

END-USE EXAMPLES Example 5

8350-1A: PE film to PE/PP bicon fabric 8326-03 (1 osy)

8350-1B: PE film to PP fabric 8326-02 (1 osy)

To demonstrate the ability of multiconstituent fabric to form afabric/film laminate, five-inch-wide fabric samples of a thermallybonded multiconstituent fiber-based nonwoven fabrics were `heat sealed`to polyethylene film. Laminate samples were prepared by heat-sealing asandwich structure composed of carded fabric (8326-02 and 8326-03)(bottom)/polyethylene film (middle)/cover fabric (8326-02) (top). Thecover fabric was used to insulate the low melting film from the sealingdie. Fabric and film dimensions were 5"×12". Time, pressure, anddie-temperature conditions were chosen that insured optimum adhesion ofthe fabric to the film while maintaining the film integrity. The heatsealer used was a Hut-Theller Precision Instruments West, Model EB(Petaluma, Calif.). Multiple heat-sealed samples were prepared bysealing across the width of the laminate sample. The die dimensions wereflat, 3/8"×5", or 1.875 square inches.

Peel strengths were determined relative to a homofil fabric laminatecontrol. Peel strengths are indicative of the level of adhesion betweenthe fabric and film layers of the laminate. Peel strengths weredetermined using an Instron Model 4201 tensile tester. Strips 1-inchwide were cut from each sealed sample. The fabric was placed in theupper grip of the tensile tester and the film in the lower grip. A gaugelength of 3-inches and a cross-head speed of 5-inches/minute were used.Peel strength properties are indicated in Table VIII. The level ofadhesion was greater for the laminate which contained themulticonstituent fiber.

Examples 6 and 7 relate to breathable liquid barrier laminates withtextile-like hand. Such laminates are suitable for use but not limitedto use as medical and industrial garments, CSR wrap, surgical drape, andhousewrap. The laminates are prepared from a layer or layers ofmicrofibrous (for example meltblown) polymer, such as polypropylene,sandwiched between two layers of nonwoven fabric containingmulticonstituent fiber according to the present invention. Thediscontinuous polymer phase of the multiconstituent fiber occupies aportion of the surface of the fiber such that both polymers of the blendare available for thermal or sonic bonding and/or lamination. The fabriccan be bonded prior to lamination or can be directly deposited on eitherside of the microfibrous layer just prior to lamination.

The microfibrous layer can be composed of meltblown fibers, wet laidpulps, or webs prepared by other known means. The microfibrous layer canbe formed prior to the lamination or extruded or formed directly ontothe multiconstituent nonwoven fabric prior to lamination. Themicrofibrous layer must be composed of a polymer which adheres to eitherthe continuous or discontinuous polymer component of themulticonstituent fiber upon thermal or sonic lamination.

Thus for instance, high melt flow isotactic polypropylene could bemeltblown into a microfibrous web and then laminated to a fabric madefrom a polymer-blend fiber having polypropylene as one of the polymerconstituents. Lamination can be with known calendering or sonic bondingtechnology. Bond pattern and processing conditions can be tailored toimpart the desired combination of strength, barrier, drape, and textileaesthetics.

EXAMPLE 6

Samples of flat-calendered `sandwich-type` laminates were prepared froma polypropylene meltblown web weighing 20 grams per square meter andhaving a nominal filament diameter of 5 microns and two outer nonwovenlayers composed of a multiconstituent fiber-based nonwoven fabric likethat described in Example 1 and identified as Sample No. 8326-03 inTable V. The three webs were simultaneously unwound from a backstand andfed continuously into a heated calender nip. The lamination was effectedusing a 22" lab calender equipped with a heated smooth rubber roll and aheated smooth steel roll. The samples were prepared at varied calenderroll surface temperatures, ranging from 318° F. to 306° F. for the steelroll and from 300° F. to 284° F., for the rubber roll. Nip pressure washeld constant at 150 pounds per linear inch (pli), and line speed washeld constant at 22 feet per minute.

Physical properties were determined for the resulting laminate samplesand are identified as sample numbers 8331-1A through 8331-1F in TableIX. It is apparent from these data (8331-1A through 8331-1F) that abreathable liquid-barrier laminate can be obtained with excellent fabrictenacity.

EXAMPLE 7

A helically-bonded `sandwich-type` laminate was prepared by a proceduresimilar to that described in Example 6, but wherein the smooth rollswere replaced with steel rolls engraved with a diagonal line patternsuch that the angle between the crisscross bond lines of the diagonalbonds opening in the machine direction (MD) measures 120 degrees, eachline measuring 60 degrees off the MD axis and such that the raisedbonding surfaces of each roll are flat and approximately 1 mm wide,separated by a recessed area measuring approximately 1.5 mm wide. Alaminate fabric was produced at 22 fpm, 150 pli, at a calender rollsurface temperature of 290° F. to 294° F.

Physical properties were determined for the fabric which is identifiedas sample number 8331-04 in Table IX. It is apparent from a comparisonof the thickness, tensile, and barrier properties of this fabric withthose in the same Table which have been flat-calendered thatsignificantly different properties can be obtained for laminatescomposed of identical starting materials. Thickness is greatly increasedover the flat-calendered samples. The loft of a fibrous web contributesto its ability to filter airborne or liquidborne particles efficiently.Air permeability is equivalent to breathability, a property associatedwith comfort in disposable garments. Air permeability combined withliquid barrier properties defines a fabric which can be used as aprotective garment in a medical or industrial end use. In addition, therange of properties exhibited by these laminates demonstrate theflexibility of multiconstituent fabrics in laminate applications.

EXAMPLE 8

By use of the isotactic polypropylene/linear low density polyethylenepolymer blend fiber-based fabric described in Table V (Sample No.8326-04C), laminates were prepared that demonstrate the flexible bondingcharacter of these novel substrates. Film and meltblown fabric wereacquired whose polymer compositions matched either that of thecontinuous phase or that of the noncontinuous phase of the polymer-blendfiber. The grades of each polymer were selected that suited therespective substrate manufacturing processes, and are therefore not theidentical polymers used in the manufacture of the multiconstituentfiber. `Sandwich-type` laminates were prepared using the proceduredescribed in Example 7.

Physical property data appears in Table X. It is apparent fromexamination of this data that laminates exhibiting excellent tensile andbarrier properties can be prepared by bonding the multiconstituentfiber-based fabric to substrates composed of a polymer selected from thesame polymer groups represented in the multiconstituent fiber.

From the above description and specific Examples of the invention, manyvariation in the webs, composites, useful products, and processes ofthis invention will be apparent to those skilled in the relevant arts.Such variations are within the scope of the present invention as measureby the apended claims.

                                      TABLE I                                     __________________________________________________________________________    BICONSTITUENT FILAMENT PROPERTIES                                                  POLYBLEND  COLD DENIER FILAMENT                                                                             ELONGATION                                      FIBER      DRAW PER    TENACITY                                                                             AT BREAK                                   DB # DESCRIPTION                                                                              RATIO                                                                              FILAMENT                                                                             (g/den)                                                                              (%)                                        __________________________________________________________________________    8319-1A                                                                            HIMONT Z30S PP                                                                           2.2  2.10   3.12   51                                                              (.10)  (.12)  (9.4)                                      8319-1B                                                                            HIMONT Z30S PP                                                                           3.5  1.95   4.72   27                                                              (.10)  (.39)  (3.7)                                      8319-2                                                                             40/60 PE(a)/PP                                                                           2    1.96   2.04   95                                                              (.11)  (.09)  (40)                                       8319-3                                                                             40/60 PE(a)/PP                                                                           3.5  1.98   3.29   33                                                              (.11)  (.39)  (7)                                        8319-4                                                                             40/60 PE(b)/PP                                                                           2    2.00   2.39   128                                                             (.10)  (.11)  (32)                                       8319-5                                                                             40/60 PE(b)/PP                                                                           3.5  1.99   3.98   39                                                              (.12)  (.20)  (4.8)                                      8319-6                                                                             PE(a)/PP + .5% NA                                                                        2    1.96   1.85   59                                                              (.12)  (.08)  (18.6)                                     8319-7                                                                             PE(a)/PP + .5% NA                                                                        3.5  1.94   3.75   35                                                              (.10)  (.17)  (5.3)                                      __________________________________________________________________________     # DENOTES STANDARD DEVIATION, WHERE n = 10.                                   PE(a)  DOW ASPUN (R) 6811, octene1/ethylene copolymer, MI = 26                PE(b)  DOW ASPUN (R) 6815, octene1/ethylene copolymer, MI = 12                PP  HIMONT Z30S Controlled Rheology Grade Polypropylene, MF = 26              NA  MILAD 5L7110 Nucleating Agent. 10% conc. in LLDPE                    

                  TABLE II                                                        ______________________________________                                        LAB TOP FABRIC PROPERTIES OF BICONSTITUENT                                    BASED THERMAL BOND FABRICS                                                    (FIBER: 40/60 PE/PP, 8319-2, 2 × DRAW, TABLE I)                         CALENDER                                                                      SURFACE                                                                       TEMPERATURE        STRIP         TEA                                          DATA   EMB.      SM.       TENSILE     (in/g/                                 BOOK # F.        F.        (g/in)                                                                              SD   % E  in2)                               ______________________________________                                        8324-1 240       244        819   87  11   116                                2      250       254       1263   55  17   224                                3      255       259       1811   86  15   317                                4      260       264       1594   48  19   302                                5      265       269       1817  185  20   347                                6      270       274       2058  184  22   451                                7      275       279       2292  100  23   484                                8      280       284       2829  141  21   554                                9      289       285       3571  177  28   821                                10     294       290       3938  215  27   804                                11     299       295       3747  355  32   930                                12     305       300       3360  272  27   686                                ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        (FIBER: 40/60 PE/PP, 8319-3, 3.5 × DRAW, TABLE I)                       ______________________________________                                        8324-13      240    245     469  53    6     49                               14           245    249     625  42    9     78                               15           250    254     765  52    9    100                               16           255    259     977  58    9    123                               17           260    264    1115 216    10   153                               18           265    269    1067 185    7    128                               19           270    274    1351 186    9    164                               20           275    279    1368  93    8    158                               21           280    284    1568 147    7    182                               22           289    285    1868 121    12   247                               23           294    290    3230 173    11   381                               24           299    295    4228 181    14   559                               25           305    300    2704 211    26   644                               ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                        (FIBER: HERCULES T-185)                                                       ______________________________________                                        8324-26      270    265     834 29     20   196                               27           280    275    1611 103    33   573                               28           290    285    2705 51     73   1757                              29           300    295    2809 361    54   1289                              30           310    305    2136 95     14   232                               ______________________________________                                         NOTES: ALL SAMPLES PRODUCED AT 500 PLI, 22 FPM, 18% BOND AREA            

                                      TABLE V                                     __________________________________________________________________________    PHYSICAL PROPERTIES OF SELECTED STAPLE BICONSTITUENTS                         __________________________________________________________________________                                             STRIP TENSILES                                FIBER SAMPLE                                                                             FIBER CALENDER       MD*        CD*                                IDENTIFICATION                                                                           DENIER                                                                              SURFACE °F.                                                                    B.W.                                                                             LOFT                                                                              (1 osy)    (1 osy)                   DATABOOK #                                                                             (TABLE I)  (dpf) E/S     (gsy)                                                                            (mils)                                                                            (g/in)                                                                            % E TEA                                                                              (g/in)                                                                            %                     __________________________________________________________________________                                                                E TEA                                                                         7                 8326-02  PP FIBER 8319-1                                                                          2     270/300 28.8                                                                             15.9                                                                              1124                                                                              35  164                                                                              288 39   78               8326-03  FIBER 8319-2, 2×                                                                   1.95  270/295 32.6                                                                             13.4                                                                              2098                                                                              24  415                                                                              501 59  256               8326-04C SAME AS ABOVE                                                                            1.95  300/300 31.6                                                                             13.3                                                                              1972                                                                              14  207                                                                              704 40  255               __________________________________________________________________________                                                     ELMENDORF                                                         GRAB TENSILES                                                                             TEAR                                                              MD    CD    MD   CD   SOFT.                                          DATABOOK #                                                                             (lbs)                                                                            % E                                                                              (lbs)                                                                            % E                                                                              (g)  (g)  (psu)              __________________________________________________________________________                                8326-02  4.8                                                                              16 2.1                                                                              33 109  144  1.7                                            8326-03  10.5                                                                             24 4.6                                                                              58 138  200  0.9                                            8326-04C 9.2                                                                              15 6.1                                                                              46  72  149  -0.8               __________________________________________________________________________

                                      TABLE VI                                    __________________________________________________________________________    PHYSICAL PROPERTIES OF SELECTED STAPLE BICONSTITUENTS                         __________________________________________________________________________                                             STRIP TENSILES                                FIBER SAMPLE                                                                             FIBER CALENDER       MD*        CD*                                IDENTIFICATION                                                                           DENIER                                                                              SURFACE °F.                                                                    B.W.                                                                             LOFT                                                                              (1 osy)    (1 osy)                   DATABOOK #                                                                             (TABLE I)  (dpf) E/S     (gsy)                                                                            (mils)                                                                            (g/in)                                                                            % E TEA                                                                              (g/in)                                                                            %                     __________________________________________________________________________                                                                E TEA                                                                         1                 8326-05  FIBER 8319-3                                                                             1.98  270/290 30.5                                                                             12.9                                                                              1293                                                                              29  173                                                                              343 43   93               8326-07  FIBER 8319-6                                                                             1.93  270/290 31 14.1                                                                              1728                                                                              27  262                                                                              464 36  131               __________________________________________________________________________                                                     ELMENDORF                                                         GRAB TENSILES                                                                             TEAR                                                              MD    CD    MD   CD   SOFT.                                          DATABOOK #                                                                             (lbs)                                                                            % E                                                                              (lbs)                                                                            % E                                                                              (g)  (g)  (psu)              __________________________________________________________________________                                8326-05  6.1                                                                              15 2.7                                                                              32 122  178  0.4                                            8326-07  8.2                                                                              18 4  40 178  228  0.7                __________________________________________________________________________

                  TABLE VII                                                       ______________________________________                                        FILAMENT AND FABRIC PROPERTIES                                                OF SELECTED MULTICONSTITUENT FIBERS                                           FILAMENT             FABRIC                                                   PROPERTIES (1)       PROPERTIES (2)                                           Fabric       Te-           Tough-            TEA                              Sample       nacity  Elong.                                                                              ness  Tensile                                                                             Elong.                                                                              (in/g/                           No. (1)                                                                             (dpf)  (gpd)   (%)   (gpd) (g/in)                                                                              (%)   in2)                             ______________________________________                                        8342-1                                                                              1.9    1.52    420   4.5   2808  74    993                              STD          (0.16)   (61) (1.0)  (251)                                                                              (17)                                   DEV.                                                                          8343-1                                                                              2.7    1.0     405   2.7   3276  30    727                              STD          (0.21)  (124) (0.8)  (377)                                                                               (6)                                   DEV.                                                                          ______________________________________                                         STD DEV: N = 10                                                               (1) 83421 Fabric: melt blend fiber composed of 40:60 wt % PE:PP               83431 Fabric: melt blend fiber composed of 40:55:5 wt. % PE:PP:EAA            (2) Fabric properties normalized to 1.0 ounce/yd2 basis weight           

                  TABLE VIII                                                      ______________________________________                                        HEAT SEAL PEEL STRENGTH                                                       FOR BICONSTITUENT-FILM LAMINATE                                                        Peel                  Peel                                                    Strength    Elongation                                                                              Strength                                       Sample   pk load     at pk     TEA                                            No.      (g/in)      (%)       (in/g/in2)                                     ______________________________________                                        8350-1A  559         24        175                                            8350-1B  443         27         86                                            ______________________________________                                         Die Geometry: 3/8" × 5", flat                                           Time: 500 msec                                                                Temp: top  245 F.; lower  245 F.                                              Pressure: 550 psi                                                        

                                      TABLE IX                                    __________________________________________________________________________    PE/PP BICONSTITUENT LAMINATES PHYSICAL PROPERTIES                             __________________________________________________________________________                             MODEL                                                                         549  LAMINATION                                                                             STRIP TENSILES (2)                          SAMPLE DESCRIPTION                                                                           B.W. THICK.                                                                             TEMP.    MD          CD                         DB # (1)            (gsy)                                                                              (mils)                                                                             (F.)     (g/in)                                                                            % E TEA (g/in)                                                                            %                      __________________________________________________________________________                                                               E TEA                                                                         0                  8331-1A                                                                            FC BICON./PPMB/BICON.                                                                        106  11.7 318/300  9078                                                                              15  1306                                                                              3940                                                                              6   250                8331-1B                                                                            "              102  9.2  316/297  9340                                                                              15  1078                                                                              4286                                                                              8   266                8331-1C                                                                            "              90   8.5  313/294  9508                                                                              16  984 3871                                                                              8   211                8331-1D                                                                            "              93   8.6  310/290  7963                                                                              11  674 4002                                                                              6   194                8331-1E                                                                            "              89   8.3  308/287  9189                                                                              14  855 4320                                                                              8   224                8331-1F                                                                            "              96   9.2  306/284  8440                                                                              14  1016                                                                              3796                                                                              18  306                8331-04                                                                            HELIC. BIC./PPMB/BIC.                                                                        86   23.6 290/294  5863                                                                              15  625 3211                                                                              17  353                __________________________________________________________________________                                       ELMENDORF                                                                             GURLEY   HYDRO-                                                       TEAR    POROSITY STATIC                                                                              MASON                                                  MD  CD  (sec)    HEAD  JAR                                               DB # (g/in)                                                                            (g/in)                                                                            (20 oz)                                                                           (5 oz)                                                                             (cm)  (sec)               __________________________________________________________________________                                  8331-1A                                                                            360 770 56  275  24.1  10                                                8331-1B                                                                            325 575 93  >5 min.                                                                            25.6  70                                                8331-1C                                                                            290 490 120 >5 min.                                                                            22.5  39                                                8331-1D                                                                            260 580 66  >5 min.                                                                            22    26                                                8331-1E                                                                            310 520 65  >5 min.                                                                            19.6  33                                                8331-1F                                                                            320 600 29  >5 min.                                                                            18.9  28                                                8331-04                                                                            330 460 inst.                                                                             7    13.2   3                  __________________________________________________________________________     NOTES:                                                                        (1) FC  FLAT CALENDERED                                                       HELIC.  CRISSCROSS BOND PATTERN FROM HELICAL ROLLS                            PPMB  POLYPROPYLENE MELT BLOWN (20 gsm)                                       BICON.  POLYETHYLENE/POLYPROPYLENE BICONSTITUENT FIBER BASED FABRIC           832603                                                                        (2) TENSILES CORRECTED TO 3 OSY UNIT WEIGHT                              

                                      TABLE X                                     __________________________________________________________________________    PHYSICAL PROPERTIES OF POLYETHYLENE/POLYPROPYLENE                             BICONSTITUENT FABRIC LAMINATES                                                __________________________________________________________________________                        CALENDER                                                                             UNIT                                                                              (3)   GRAB TENSILES                            SAMPLE              TEMP. (2)                                                                            WT. CALIPER                                                                             MD El.                                                                              CD El.                             NO.   DESCRIPTION (1)                                                                             (F.)   (gsy)                                                                             (mils)                                                                              (lbs)                                                                            (%)                                                                              (lbs)                                                                            (%)                             __________________________________________________________________________    8333-05                                                                             BICON/PE FILM/BICON                                                                         252/263                                                                              76.6                                                                              28.1  22 27 11.7                                                                             38                              8333-06                                                                             BICON/PP FILM/BICON                                                                         287/288                                                                              70.9                                                                              26.4  22.7                                                                             30 11.1                                                                             42                              8333-04                                                                             BICON/PE-MB/BICON                                                                           268/260                                                                              93.6                                                                              26.8  23.1                                                                             24 10.2                                                                             34                              8331-04                                                                             BICON/PP-MB/BICON                                                                           290/294                                                                              86.3                                                                              27.2  25.3                                                                             25 10.8                                                                             36                              __________________________________________________________________________                                 (4)                                                               ELM.        GURLEY   (5)  HYDRO-                                              TEAR  MULLEN                                                                              POROSITY MASON                                                                              STATIC                                        SAMPLE                                                                              MD CD BURST (5 oz)                                                                            (20 oz)                                                                            JAR  HEAD                                          NO.   (g)                                                                              (g)                                                                              (psi) (sec)    (sec)                                                                              (cm)                               __________________________________________________________________________               8333-05                                                                             400                                                                              540                                                                              21    NR  53.3 3.16 18.4                                          8333-06                                                                             330                                                                              430                                                                              19    NR  98   163  23.7                                          8333-04                                                                             350                                                                              400                                                                              20    1.57                                                                              NR   inst.                                                                              16.1                                          8331-04                                                                             320                                                                              380                                                                              19    7.1 NR   3    13.2                               __________________________________________________________________________     NOTES:                                                                        ALL PE IS 1OCTENE, LINEAR LOW DENSITY POLYETHYLENE, UNLESS OTHERWISE          STATED                                                                        (1) BICON -- BICONSTITUENT FIBERBASED FABRIC (832604 CARDED THERMALBOND,      40:60, PE:PP), 1 OSY                                                          PE FILM -- LOW DENSITY POLYETHYLENE FILM OBTAINED FROM EDISON PLASTIC, 1      MIL.                                                                          PPFILM -- POLYPROPYLENE FILM OBTAINED FROM EDISON PLASTIC, 1 MIL              PEMB -- POLYETHYLENE MELTBLOWN FABRIC, 20 GSM                                 (2) CALENDER -- HELICAL STEEL/HELICAL STEEL, NIP PRESSURE = 350 PLI, LINE     SPEED = 12.5 FPM                                                              (3) FABRIC CALIPER MEASURED USING A 551M CALIPER TESTER                       (4) NR -- NO READING, PROCESS EITHER TOO FAST OR TOO SLOW FOR ACCURATE        MEASUREMENT                                                                   (5) INST -- INSTANTANEOUS                                                

I claim:
 1. A strong thermally-bonded nonwoven fabric having a basisweight in the range of 5 grams per square meter through 100 grams persquare meter made from a web that comprisesfrom 100 to 5 percent byweight of one or more multiconstituent fibers having a fineness of 5 to50 microns, wherein said multiconstituent fibers are composed of highlydispersed blends of at least two different immiscible thermoplasticpolymers and have a dominant continuous polypropylene polymer phase inwhich is dispersed two discontinuous phases, one composed of linear lowdensity polyethylene and the other of ethylene/acrylic acid copolymer,wherein the polymer of said noncontinuous phase or phases has a PolymerMelting Temperature (PMT) at least 30° C. below the PMT of saidcontinuous phase, wherein the mean of the cross-sectional areas of saidnoncontinuous phase or phases is less than 0.1% of the cross-sectionalarea of said multiconstituent fibers, and wherein said multiconstituentfibers are configured such that said noncontinuous phase or phasesoccupy a substantial portion of the fiber surfaces, from 0 to 95 percentby weight of other fibers and a multiplicity of thermal bonds bondingthe fibers of the nonwoven fabric, said thermal bonds being formed bysaid low melting noncontinuous phase of said multiconstituent fiber. 2.A fabric according to claim 1 which has been formed by a procedureselected from the group consisting of carding/thermal bonding,spunbonding, wetlaying/thermal bonding, centrifugalspinning/spunbonding, wetlaying/hydroentangling/thermal bonding, andcarding/hydroentangling/thermal bonding.
 3. A pattern-bonded fabricaccording to claim
 2. 4. A flat-calender-bonded fabric according toclaim
 2. 5. A fabric according to claim 1 that consists essentially of100% of said multiconstituent fibers.
 6. A fabric according to claim 1that consists essentially of from 50 to 5% by weight of saidmulticonstituent fibers and from 50 to 95% by weight of other textilefibers.
 7. A fabric according to claim 1 having a basis weight in therange of from about 15 grams per square meter through about 55 grams persquare meter.
 8. A fabric according to claim 7 in which saidmulticonstituent fibers have a fineness of 10 to 30 microns and a roundcross-sectional profile.
 9. A fabric according to claim 7 in which saidmulticonstituent fibers have a fineness of 10 to 30 microns and aflattened cross-sectional profile.
 10. A fabric according to claim 7 inwhich said multiconstituent fibers have a fineness of 1-10 denier and asurface to volume ratio greater than 0.6.
 11. A fabric according toclaim 1 which one or more of the polymers which comprise saidmulticonstituent fiber contain a nucleating or clarifying agent selectedfrom the group consisting of substituted-sorbitols, acrylic acidmodified polypropylenes, organic acids, sodium benzoate, and stearates.12. A fabric according to claim 1 which one or more of the polymerswhich comprise said multiconstituent fiber contain an additive oradditives selective from the group consisting of antioxidants, thermalstabilizers, gamma ray stabilizers ultraviolet stabilizers, flameretardants, antistatic agents, Ti02, talc, pigments, dyes, hydrophilicsurfactants, hydrophobic agents, antiblocking agents, andelectrically-conductive fillers.
 13. A thermally-bonded nonwoven fabricaccording to claim 1, wherein the continuous polypropylene polymer phaseis an isotactic polypropylene polymer phase having melt flow rate of 4to 100 g/min.
 14. The thermally bonded nonwoven fabric according toclaim 6, wherein said other fibers have fineness of 10 denier or lower.15. The thermally-bonded nonwoven fabric according to claim 6, whereinsaid other fibers are selected from the group consisting of cottonfibers, viscose rayon fibers, acrylic fibers, wool fibers, polypropylenefibers, polyethylene fibers, polyester fibers, polyamide fibers,polyaramid fibers, carbon fibers, chitin fibers, multicomponent fibers,and mixtures thereof.
 16. A nonwoven fabric laminate comprising: athermally-bonded nonwoven web that comprises from 100 to 5 percent byweight of one or more multiconstituent fibers having a fineness of 5 to50 microns, and from 0 to 95 percent by weight of other fibers;saidmulticonstituent fibers being composed of highly dispersed blends of atleast two different immiscible thermoplastic polymers which are presentas a dominant continuous polypropylene phase in which is dispersed twodiscontinuous phases, one composed of linear low density polyethyleneand the other of ethylene/acrylic acid copolymer, with the polymer ofsaid noncontinuous phase or phases having a Polymer Melting Temperature(PMT) of at least 30° C. below the PMT of said continuous phase, and themean of the cross-sectional area of said noncontinuous phase or phasesbeing less than 0.1% of the cross-sectional area of saidmulticonstituent fibers, and said multiconstituent fibers beingconfigured such that said noncontinuous phase or phases occupy asubstantial portion of the fiber surfaces; said thermally bonded webincluding a multiplicity of thermal bonds bonding the fibers of thenonwoven web, with said thermal bonds being formed by said low meltingnoncontinuous phase of said multiconstituent fibers; and at least oneother web laminated to said thermally bonded nonwoven web and adheringto the continuous or noncontinuous polymer phases of themulticonstituent fibers of said thermally bonded nonwoven web.
 17. Anonwoven fabric laminate according to claim 16, wherein said at leastone other web comprises at least one polyolefin film.
 18. A nonwovenfabric laminate according to claim 17, wherein the laminate comprises adiaper backsheet.
 19. A nonwoven fabric laminate according to claim 17,wherein said polyolefin film comprises a linear low density polyethylenefilm.
 20. A nonwoven fabric laminate according to claim 19, wherein saidthermally bonded nonwoven web consists essentially of from 50 to 5% byweight of said multiconstituent fibers and from 50 to 95% by weight ofother textile fibers.
 21. A nonwoven fabric laminate according to claim16, wherein said at least one other web comprises at least onemicrofibrous layer.
 22. A nonwoven fabric laminate according to claim21, wherein said microfibrous layer is a polyolefin meltblown.
 23. Anonwoven fabric laminate according to claim 21 wherein said microfibrouslayer is a wetlaid polyolefin synthetic pulp.
 24. A nonwoven fabriclaminate according to claim 16, wherein said thermally bonded nonwovenweb consists essentially of 100% by weight of said multiconstituentfibers.
 25. A nonwoven fabric laminate according to claim 16, whereinone or more of the polymers which comprise said multiconstituent fibercontain a nucleating or clarifying agent selected from the groupconsisting of substituted-sorbitols, acrylic acid modifiedpolypropylenes, organic acids, sodium benzoate, and stearates.
 26. Astrong thermally-bonded nonwoven fabric made from a web thatcomprisesfrom 100 to 5 percent by weight of one or more multiconstituentfibers having a fineness of 5 to 50 microns, and from 0 to 95 percent byweight of other fibers; said multiconstituent fibers being composed ofhighly dispersed blends of at least two different immisciblethermoplastic polymers, including a dominant continuous polypropylenephase in which is dispersed two noncontinuous phases, one composed oflinear low density polyethylene and the other of ethylene/acrylic acidcopolymer, with the polymers of said noncontinuous phases having aPolymer Melting Temperature (PMT) of at least 30° C. below the PMT ofsaid continuous phase, and the mean of the cross-sectional area of saidnoncontinuous phase or phases being less than 0.1% of thecross-sectional area of said multiconstituent fibers, and saidmulticonstituent fibers being configured such that said noncontinuousphases occupy a substantial portion of the fiber surfaces; said fabricincluding a multiplicity of thermal bonds bonding the fibers of thenonwoven fabric, with said thermal bonds being formed by said lowmelting noncontinuous phase of said multiconstituent fiber.